The present invention relates generally to flexible sensors and, more particularly, to a flexible sensor for measuring flow and temperature through detection of vortex shedding i.e., von Kármán vortex street.
Vortex frequency flow meters utilize the periodic vortex shedding of a blunt obstruction i.e., a bluff body located in the fluid and flow. The phenomenon exists that vortices are shedded in alternating opposing sides of the blunt obstruction or bluff body. Therefore, a so-called von Kármán vortex street is created by the vortices. The vortices remain active for a certain distance behind the obstruction in the flow before being dissolved due to viscosity. For certain obstructions there exists a relationship between the frequency of vortex shedding and the speed of fluid flow. In other words, the speed of fluid flow can be directly derived from determining the frequency of vortex shedding. Vortex sensors used for determining vortex sheddings may be used to identify other parameters of the flowing fluid.
Numerous methods and apparatuses have been designed for measuring vortex streets in order to determine the flow of fluid through piping. One apparatus is a thermal sensor i.e., hot wire. Thermal sensors measure cooling rates resulting from the passage of vortices across the bluff body and the sensor. Another apparatus implements a magnetic pick-up disk or shuttle-type sensing element which detects vibrations of the disk or shuttle element based on the pressure pulses of the vortex street. Several vortex sensors implement piezo electric crystals or piezo resistant systems as has been described in great detail by several references. Each of these systems has its own limitations, advantages, and disadvantages.
According to an illustrative embodiment, the present disclosure provides a vortex sensor for detecting the flow volume of a fluid. The vortex sensor includes a housing defining a housing cavity for the fluid to flow. The vortex sensor includes an obstruction supported by the housing. The obstruction is mounted in the housing cavity. The obstruction is perpendicular to the flow of the fluid. The obstruction includes a plurality of side edges configured to generate alternating vortices in the fluid. The vortex sensor includes a flexible deflection sensor supported by the obstruction. The flexible deflection sensor has a longitudinal axis downstream of the obstruction. The flexible deflection sensor is configured to be located between the alternating vortices in the fluid. The flexible deflection sensor includes a flexible insulating substrate and a conductive material applied to the flexible insulating substrate. The conductive material has an electrical resistance which varies as the conductive material is bent.
According to a further illustrative embodiment, the present disclosure includes a vortex sensor for detecting the flow volume of a fluid and for detecting the temperature of the fluid. The vortex sensor includes a housing defining a housing cavity for the fluid to flow. The vortex sensor includes an obstruction supported by the housing. The obstruction is mounted in the housing cavity. The obstruction is perpendicular to the flow of the fluid. The obstruction includes a plurality of side edges configured to generate alternating vortices in the fluid. The vortex sensor includes a flexible deflection sensor supported by the obstruction. The flexible deflection sensor has a longitudinal axis downstream of the obstruction. The flexible deflection sensor is configured to be located between the alternating vortices in the fluid. The flexible deflection sensor includes a flexible insulating substrate having a glass transition temperature generally below a range of approximate temperatures of the fluid. The flexible insulating substrate includes a linear material. The flexible deflection sensor includes a conductive material applied to the flexible insulating substrate. The conductive material has an electrical resistance which varies as the conductive material is bent.
According to a further illustrative embodiment, the present disclosure includes a method of detecting the flow volume of a fluid. The method comprises the step of providing a flexible deflection sensor supported by an obstruction. The flexible deflection sensor and the obstruction are mounted within a housing cavity defined by a housing. The flexible deflection sensor is located downstream of the obstruction. The flexible deflection sensor includes a conductive material having an electrical resistance which varies with an amount of bending of the conductive material. The method comprises the step of providing the flow of the fluid through the housing cavity. The method comprises the step of generating alternating vortices in the fluid. The method comprises the step of applying an electrical signal to the conductive material. The method comprises the step of measuring variation in the electrical resistance. The method comprises the step of analyzing the frequency of the variation to determine the flow volume of the fluid.
Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.
Corresponding reference characters indicated corresponding parts throughout the several views. Although the drawings represent embodiments of the present disclosure, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present disclosure. Although the exemplification set out herein illustrates embodiments of the disclosure, in several forms, the embodiments disclosed below are not intended to be exhaustive or to be construed as limiting the scope of the disclosure to the precise forms disclosed.